Progress 01/01/05 to 12/31/09
Outputs
OUTPUTS: The objectives of this project were completed by producing soymilk from whole dehulled beans to retain all essential solids. We investigated the effect of continuous flow high pressure throttling (CFHPT) process on the shelf life of soymilk and injured microorganisms. The reduction of C. sporogenes in soymilk increased as the hold time, pressure and temperature were increased. Inactivation of C. sporogenes was higher at 276 MPa as compared to 207 MPa when the exit temperature was 121 oC and hold time was 20.8 s. At 276 MPa and the residence time of 20.8 s, log reduction increased to 5.8, and almost complete inactivation was achieved when the exit temperature was 145 oC for both 207 and 276 MPa. The heat resistance of C. sporogenes by capillary tube method in soymilk and 0.1% peptone water showed significant increase when heated in soymilk in comparison to 0.1% peptone water. The D121 value for C. sporogenes in 0.1% peptone water was 3-folds less than that in soy milk. The z value observed was also lower in peptone than in soy milk. The D121 value calculated for soymilk was 1.5 min and that for 0.1% peptone water was 0.54 min. Injury was observed more at 207 MPa as compared to 276 MPa suggesting that at lower pressure and temperature a large number of spores were injured while at high pressure and high temperature no recoverable injured spores were observed. Results also indicate that an increasing number of spores were destroyed due to pressure treatment and the destruction increased with both temperature and hold time. Finally, at higher pressure and temperature, the counts were undetectable indicating that spores were present. The soymilk was also characterized for particle size distribution, rheological and ultra-structural properties, to model and evaluate the consumer acceptability. The combined process Megatron (M) and CFHPT treated samples at the highest pressure showed the smallest particle size and the highest apparent viscosity. All samples showed pseudoplastic behavior. Ultrastructural images elucidated particle microstructure in the soymilk and homogeneity of suspended particles. The very small fat globules at highest CFHPT pressure of process M were seen entrapped in the network and were uniformly distributed. The increase in the CFHPT flow rate significantly affected size reduction of particles of soymilk. The models were established and used to predict the size of particles in soymilk, at different volume fractions. Consumer acceptability test showed that more research is needed to make a soymilk that appeal to the taste of the American consumer before the CFHPT process can be used commercially. Thus, soymilk with all the essential solids can be made available to the public and processors benefit from the high processing yields since none of the essential solids of the beans are discarded. The outcomes of this process are being used by several small beverage companies to produce functional (nutraceutical) drinks. The outcome helped another graduate student to apply the results for dairy milk processed under CFHPT. The results have been presented in several professional conferences and demonstrated to food industry clients. PARTICIPANTS: Dr. Romeo Toledo was Co-PI on this project. Mr. Carl Ruiz, Research Professional helped on the pilot scale trials. Several graduate students helped the two main students, Litha Sivanandan and Vijendra Sharma to complete their projects. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
The continuous high pressure throttling (CFHPT) process helped in reduction of particle size of soymilk. The particle size of soymilk sterilized using this system can be predicted by using the empirical model developed in this study and applied to other similar products. The particles in soymilk were reduced to a level so that there was no apparent separation in the soymilk after a month of storage at 4 C which is desired by the industry. The high pressure throttling process helped in utilizing the whole bean solid to produce excellent quality soymilk with high emulsion stability and without use of added emulsifiers. The mouthfeel, flavor and color qualities were excellent. Thus combined process Megatron (M) and the highest CFHPT pressure were considered the best treatment for inactivating the microorganisms. The high pressure caused microbial cell injury while the temperature rise due to thee pressure drop caused the cell death. This combination of process required relatively low temperature throughout the process except for less than 20 s when the temperature rise occurred and that is the reason for better quality product. Therefore, this process allows utilization of the whole soybean to produce excellent quality soymilk with high emulsion stability. The same process with some modification is being used for making emulsified (omega 3) nutraceutical beverages.
Publications
- Sivanandan, L., Toledo, R.T. and Singh, R.K. 2008. Effect of continuous high-pressure throttling on rheological and ultrastructural properties of soymilk. Journal of Food Science 73(6): E288-E296. Sharma, V., Singh, R. K., and Toledo, R. T. 2009. Microbial inactivation kinetics in soymilk during continuous flow high-pressure throttling. Journal of Food Science 74(6): M268-M275. Sivanandan, L. 2007. Characterization of soymilk produced by continuous flow high pressure throttling, Ph. D. Dissertation, University of Georgia, Athens, GA. Sharma, V. 2008. Microbial inactivation kinetics in soymilk during continuous flow high pressure throttling system. M.S. Thesis, University of Georgia, Athens, GA
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Progress 01/01/08 to 12/31/08
Outputs
OUTPUTS: To study the death kinetics of microorganisms, Clostridium Sporogenes (PA3679) spores were grown and harvested. The spores were inoculated in the soymilk sample and assessed for their concentration prior to the high pressure processing. We investigated the effect of CFHPT process on the shelf life of soy milk and determination of injured microorganisms. Soy milk was pressurized at 207 and 276 MPa at four different exit temperatures (85, 121, 133 and 145 oC) and (102, 121, 133, and 145 oC) respectively at three different flow rates (0.75, 1.0, and 1.50 L/min). Hold time calculated for these three flow rates was (20.8, 15.6, and 10.4 s) respectively. We found that log reduction of C. sporogenes in soymilk increased as the hold time, pressure and temperature were increased. Inactivation of C. sporogenes was higher at 276 MPa as compared to 207 MPa when the exit temperature was 121 oC and hold time was 20.8 sec. At 207 MPa, log reductions from 0.4 to 5.6 were observed at different exit temperatures (85, 121, 133, and 145 oC) and different residence time in the holding tube (10.4, 15.6, and 20.8 s). Similarly at 276 MPa and the residence time of 10.4, 15.6, and 20.8 s log reduction increased from 0.85 to 5.8 at different exit temperatures (102, 121, 133, and 145 oC). Almost complete inactivation was achieved when the exit temperature was 145 oC for both 207 and 276 MPa. We also determined the heat resistance of C. sporogenes by capillary tube method in soymilk and 0.1% peptone water. A significant increase in heat resistance was observed in Clostridium sporogenes spores when heated in soymilk in comparison to 0.1% peptone water. The D121 value for C. sporogenes in 0.1% peptone water was 3-folds less than that in soy milk. The z value observed was also lower in peptone than in soy milk. The D121 value calculated for soymilk was 1.5 min and that for 0.1% peptone water was 0.54 min.Injury was observed more at 207 MPa as compared to 276 MPa suggesting that at lower pressure and temperature a large number of spores were injured while at high pressure and high temperature no recoverable injured spores were observed. PARTICIPANTS: One Ph. D. student, Litha Sivanandan spent two months in 2008 to fine tune the system after completing her Ph. D. in December 2007. Another student, Mr. Vijendra Sharma completed his Master degree and started Ph. D. TARGET AUDIENCES: A poster was presented in the annual meeting of Institute of Food Technologists, which provided exposure of this research to a broad audience from academia and industry. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
The microbial destruction rate is used for calculation of process time and prediction of the quality of soymilk processed under continuous high pressure. The results show that the combination of high pressure and heat generated due to throttling of pressure was sufficient to destroy the target microorganisms. Our results also indicate that an increasing number of spores were destroyed as a result of pressure treatment and the destruction increased with both temperature and hold time. Finally, at higher pressure and temperature, the counts were undetectable indicating that spores were present but subsequently destroyed during processing.
Publications
- Sivanandan, L., Toledo, R.T. and Singh, R.K. (2008). Effect of Continuous High-pressure Throttling on Rheological and Ultrastructural Properties of Soymilk. Journal of Food Science 73(6): E288-E296.
- Sharma, V. 2008. Microbial inactivation kinetics in soymilk during continuous flow high pressure throttling system. M. S. Thesis, University of Georgia, Athens
- Sharma, V., Singh, R. K. and Toledo, R. T. 2008. Microbial inactivation kinetics in soymilk during continuous flow high pressure throttling. Poster presented at the Annual Meeting of Institute of Food Technologists, New Orleans, LA.
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Progress 01/01/07 to 12/31/07
Outputs
A procedure for making soy milk from whole de-hulled soybeans by continuous flow high pressure throttling (CFHPT) sterilization was developed and the effects of different pressures and flow rates of the CFHPT system in the temperature rise and particle size distribution of soymilk were studied. Soybeans were dehulled by heating for 5 min on a pan in an impinger oven at 154.44 C. The tempered soybeans were coarse ground in a plate mill with the plates set far enough apart to crack the hulls but not to break the cotyledons. The hulls and the cotyledons were separated by air classification. Soymilk was prepared from whole dehulled soybeans by blanching in deionized water (DIW) at 60 C for 2.5 hours. The blanched cotyledons were drained, rinsed 3 times with DIW and the mixture (3 times DIW) was ground in a food processor. Then comminution was done in Megatron. The comminuted suspension was pressurized at 68.95, 103.42, 137.90, 206.84, or 275.79 MPa using a pressure
intensifier in the CFHPT system and after heating to 80 C using a tube heat exchanger; it was throttled down to atmospheric pressure. After throttling, a minimum back pressure of 350 kPa was applied to avoid flashing of vapors at the outlet. Between throttling valve and back pressure valve a holding tube allowed the fluid to be at the elevated temperature at depressurization for 5 seconds minimum. This temperature was measured using a thermocouple at the end of the holding tube. The soymilk samples were collected at a volumetric flow rate of 0.75, 1.00, and 1.50 L/min from CFHPT system. The sterilized soymilk was immediately cooled to 4 C or below by passing it through another heat exchanger coil immersed in an ice bath. After collecting the sample, it was kept in ice to further reduce its temperature and to avoid the heat-induced changes in the product. Application of higher pressures improved flow properties of soymilk by narrowing down the distribution area of particles of similar
diameter. There was no significant difference in total solid content among the treatment samples. The results showed that there existed a significant effect of flow rate through the CFHPT on the particle size suspended in soymilk. Significant decrease in particle size of soymilk was obtained by increasing pressure of CFHPT system. A model was established, for the soymilk processed using CFHPT process, and the model can be effectively used for predicting the particle size diameter (um) at a particular pressure (MPa) and volume fraction (%) of particles. The flow rates at a particular pressure in CFHPT process did not result in a significant difference in temperature rise of the product. The observed temperature rise was directly proportional to the applied pressure in the CFHPT system. This temperature rise might have contributed to the particle size reduction by facilitating the rupture of the particles at high turbulence, shear, and cavitation occurred at and after the throttling
valve.
Impacts
The high pressure throttling process helped in reduction of particle size of soymilk. In CFHPT process, increases of flow rate and pressure application are effective in reducing the particle size. The particle size of soymilk sterilized using CFHPT system can be predicted by using the empirical model developed in this study. The particles in soymilk were reduced to a level so that there was no apparent separation in the soymilk after a month of storage at 4 C. The high pressure throttling process will help in utilizing the whole bean solid to produce excellent quality soymilk with high emulsion stability.
Publications
- Sivanandan, L. 2007. Characterization of soymilk produced by continuous flow high pressure throttling process. Ph. D. dissertation, University of Georgia, Athens pp 187.
- Sivanandan, L, Toledo, RT, Singh, RK. 2007. Effect of Continuous Flow High Pressure Sterilization on Properties of Soymilk. (Abstract) Annual Institute of Food Technologists meeting, Chicago, IL. Jul-Aug (2007.
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Progress 01/01/06 to 01/01/07
Outputs
PROGRESS: 2006/01 TO 2006/12 A procedure for making soy milk from whole de-hulled soybeans by continuous flow high pressure throttling (CFHPT) sterilization was developed and the best treatment was selected according to particle size distribution, ultra-structural and rheological properties tested. Soybeans were dehulled by heating for 5 min on a pan in an impinger oven at 154.44 C. The tempered soybeans were coarse ground in a plate mill with the plates set far enough apart to crack the hulls but not to break the cotyledons. The hulls and the cotyledons were separated by air classification. Soymilk was prepared from whole dehulled soybeans by blanching in deionized water (DIW) at 60 C for 2.5 hours. The blanched cotyledons were drained, rinsed 3 times with DIW and the mixture (3 times DIW) was ground in a food processor. Then comminution was done in Megatron or Fitzpatrick mill or Stone mill. The comminuted suspension was pressurized at 68.95, 103.42, 137.90, 206.84,
or 275.79 MPa using a pressure intensifier in the CFHPT system and after heating to 80 C using a tube heat exchanger; it was throttled down to atmospheric pressure. After throttling, a minimum back pressure of 350 kPa was applied to avoid flashing of vapors at the outlet. Between throttling valve and back pressure valve a holding tube allowed the fluid to be at the elevated temperature at depressurization for 5 seconds minimum. This temperature was measured using a thermocouple at the end of the holding tube. The sterilized soymilk was immediately cooled to 4 C or below by passing it through another heat exchanger coil immersed in an ice bath. After collecting the sample, it was kept in ice to further reduce its temperature and to avoid the heat-induced changes in the product. Application of higher pressures improved flow properties of soymilk by narrowing down the distribution area of particles of similar diameter. There was no significant difference in total solid content among the
treatment samples. Megatron-CFHPT processed samples were having the smallest particle size and were more viscous than other samples. At 275.79 MPa cryo scanning electron microscopy (cryo-SEM) image showed the particle distribution was good throughout the area, however, the particles were still not separated at the lowest pressure treatment. Cryo-SEM images contributed in identifying the best sample. From the images, Megatron-CFHPT sample processed at 275.79 MPa was selected as the best treatment. Multiphoton confocal scanning laser microscope images showed the distribution of fat and protein in soymilk. The protein particles could not be identified individually due to very small particle size and distribution. The fat globules were also very small in size. We feel that the process of dehulling, blanching, coarse comminution in a rotary blade comminutor followed by fine comminution in a Megatron is an effective procedure for preparing soymilk to be used in the high pressure
sterilization experiments.
Impacts
The results showed significant differences in particle size distribution between the soymilk samples processed by one pass and two pass (double) homogenization. Particle size was reduced and particle settling was reduced as homogenization pressure increased. Ultra-structural measurements showed that particles hydrated better when the suspension was hydrated before homogenization. Samples with only one pass homogenization showed uneven and unbroken particle structure. Rheological properties of the soymilk samples were measured at different temperatures (4 C, 10 C, and 25 C) and results indicate that the samples heated before homogenization had higher viscosity than the unheated samples. Total soymilk solids have to be standardized because vaporization of moisture during heating changes solids content. All the samples showed non-Newtonian pseudoplastic behavior and increasing temperature caused decrease in viscosity. The flow behavior index was relatively constant for
all the treatments which confirmed that there was no chemical change during the process. Arrhenius model expressed the temperature dependence of apparent viscosity. The new process results in better tasting more nutritious soymilk than those produced using the traditional methods.
Publications
- No publications reported this period
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Progress 01/01/05 to 12/31/05
Outputs
A procedure for making soy milk from whole de-hulled soybeans was developed. Soybean cultivar was Benning Group VII obtained from the Georgia Seed Development Commission. Seeds were de-hulled by drying in an impingement oven 5 min. at 310 F (154 C) followed by cooling, rubbing the hulls through a plate mill followed by air classification. De-hulled beans were re-hydrated by blanching in de-ionized water at 60 C for 2.5 h. Beans were cold water rinsed, re-suspended in cold water and comminuted through a Robot Coupe food processor. The suspension with still a few large visually discernible particles was further comminuted through a Fitzmill in two passes, first through 0.0050 in. screen and a second pass through a 0.0020 in. screen. One group of samples was prepared from the cold suspension by homogenizing in a Gaulin standard homogenizer at 14,000 psi in either one or two passes. Another group was prepared by heating the Fitzmil comminuted suspension at 100 C for 15
min. followed by two-pass homogenization in a Gaulin at 14,000 psi. Another set of samples from the Fitzmill comminuted suspension was homogenized at 10000, 15000, 20,000, 30000, and 37000 psi in one pass through a microfluidizer with a needle valve pressure reducing valve. Another method of comminution employed a high speed stone mill instead of the Fitzmill and homogenization through the microfluidizer. It is important that the particle size of the suspended soybean fragments is small enough to prevent clogging of the orifice in the needle valve used for pressure reduction. All soymilk were standardized to the same suspended solids content and subjected to rheological analysis. Gaulin homogenized samples pre-heated to 100 C prior to comminution were more viscous than those homogenized cold. Microfluidized samples at 20,000 psi and higher were more viscous than the Gaulin homogenized samples even when no heating was done prior to microfluidizer homogenization. All microfluidized
samples prepared using the Fitzmill had less apparent viscosity at the same shear rate than those prepared using the high speed stone mill. Thus suspended particle size was smaller in the stone mill comminuted milk than that from the Fitzmill. Samples microfluidized at 30,000 and 37,000 psi were more viscous than those of their counterparts microfluidized at 20,000 psi and below. We feel that the process of dehulling, blanching, coarse comminiution in a rotary blade comminutor followed by fine comminution in a stone mill is an effective procedure for preparing soymilk to be used in the high pressure sterilization experiments.
Impacts
The whole soybean except for the hulls was effectively utilized in making soy milk with comparable particle size distribution and more viscous consistency than milk produced by hot water extraction of the beans. All of the nutrients and beneficial phytochemical components are preserved in the milk using this method of preparation. The use of a stone mill and high pressure homogenization is new in a the process of producing soymilk that has more beneficial constituents than the standard commercial process used today.
Publications
- No publications reported this period
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